1. Field of the Invention
The present invention relates to a radiation imaging apparatus and a processing method therefor.
2. Description of the Related Art
A radiation imaging apparatus is known, which obtains a radiographic image based on the detection of radiation (e.g., X-rays) transmitted through an object. For example, the radiation imaging apparatus obtains images of an imaging target such as the alimentary canal with radiation. Radiation imaging apparatuses are widely used in routine health checkups and the like as well as examinations at the time of medical treatment.
Radiation imaging apparatuses are available in various forms. As disclosed in, for example, Japanese Patent Laid-Open No. 2005-27806, there is available an apparatus which fluoroscopes and images an object, with the object placed on the top panel of a bed that is positioned between an X-ray generator and an X-ray detector mounted on the two ends of a supporting member called a C-arm. The X-rays emitted from the X-ray generator pass through the object and strike the X-ray detector. The X-ray detector converts the X-rays transmitted through this object into an optical signal. Executing this operation under predetermined X-ray irradiation conditions can allow display of a fluoroscopic image of an object on a monitor in real time.
In the above X-ray imaging apparatus, the operation steps associated with fluoroscopy and imaging performed by an operator are roughly classified into 1) positioning while performing fluoroscopy, 2) diagnosis in fluoroscopic state (check on an imaging target), and 3) imaging of a positioned target.
In portion 1), positioning while performing fluoroscopy, positioning is performed to display an imaging target in a desired size at a proper position (e.g., a middle position) on a monitor. In such positioning, the operator moves the X-ray generator, the X-ray detector, and the top panel. That is, since the operator moves them during positioning, the fluoroscopic image (observed image) displayed on the monitor moves.
In contrast to this, in portion 2), diagnosis in fluoroscopic state (checking on the imaging target), the operator does not perform a positioning operation, and the observed image on the monitor is therefore fixed. Thereafter, when the operator visually checks the imaging target, the apparatus executes portion 3), imaging of the positioned target, under predetermined X-ray irradiation conditions. As described above, when performing X-ray imaging, operation steps 1) to 3) are repeated.
In general, in a medical situation using X-rays, important management and study items include: how to shorten the time required for fluoroscopy and imaging and how to reduce the X-ray exposure dose for the subject (herein, the patient may sometimes be referred to as the “subject”, and the particular portion of the body being studied may is sometimes termed the “object”).
In, for example, the positioning while performing fluoroscopy, if a region of an image displayed on the monitor is suitable for the positioning operation, the operator can easily find the imaging target, and hence it is possible to shorten the time required for positioning. In addition, if the apparatus is configured not to image unnecessary regions which do not contribute to the positioning operation for the imaging target, it is possible to reduce the X-ray exposure dose delivered to the patient.